<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }


        ul {
            list-style: none;
            width: 2400px;
        }


        #box {
            width: 1200px;
            height: 400px;
            border: 1px solid red;
            margin: 100px auto;
            overflow: hidden;
        }


        #box li {
            width: 100px;
            height: 400px;
            float: left;
            transition: all 0.5s ease-out;
        }


        #box li.over {
            width: 800px;
        }
    </style>
    <script src="./app.vue"></script>
</head>

<body>
    <div id="box">
        <ul>
            <li v-for="(item,index) in list" :class="{ over:overIndex==index }" @mouseover="doOver(index)">
                <img :src="list[index]" alt="" />
            </li>
        </ul>
    </div>
</body>
<script>
    let app = new Vue({
        el: '#app',
        data: {
            list: []
        }
    })
</script>

</html>